Hubble Space Telescope

The $2 billion Edwin P. Hubble Space Telescope (HST) was lifted into
orbit by the space shuttle Discovery on April 24, 1990. Weighing
approximately 25,500 lb (11,000 kg) and measuring 43 ft (13 m) long by 14
ft (4 m) wide, or roughly the size of a school bus, HST is the most
complex and sensitive space observatory ever constructed, and it has
become astronomers' principal tool for exploring the universe.

During its lifetime, the space telescope has required intermittent
servicing. In June 1990, just two months after HST was launched into
orbit, astronomers discovered that there was a spherical aberration in one
of the telescope's mirrors. In 1991, two of the craft's six gyroscopes
failed, and a third failed on Nov. 18, 1993, causing additional problems.
NASA successfully repaired the space telescope during the Dec. 2–13, 1993,
mission of the Endeavour.

Crew members of the space shuttle Discovery made fresh repairs
to the telescope during an upgrade mission in Feb. 1997 and installed two
powerful new scientific instruments–the Near Infrared Camera and
Multi-Object Spectrometer (NICMOS)–giving HST still sharper and more
distant views of the universe. The Near Infrared Camera can see the
universe at near infrared wavelengths more sensitively that any other
existing or planned telescope.

The third servicing mission by the crew of Discovery in Dec.
1999 extended the telescope's scientific power with new instruments and
repaired its optics, solar arrays, gyros, and other components. A fourth
servicing mission was carried out by astronauts aboard the space shuttle
Columbia in March 2002. This time, the upgrades to the Hubble
included a new power control unit, a powerful new camera, and solar array
panels.

A fifth servicing mission, scheduled for July 2003, was canceled after the
Columbia space shuttle disaster. Without servicing, Hubble was expected
to be out of commission by 2008, but was granted a reprieve with a final servicing
mission in May 2009. The telescope's status is now listed as "extended mission in
progress."

After NASA announced that the telescope would not be repaired due to
the risks to a human crew, outcry from scientists, politicians, and the
public forced the agency to consider sending a robotic repair mission. In
July 2004, a panel from the National Academy of Sciences urged NASA to
save the Hubble, voicing a preference for a staffed mission. The telescope
repair mission has been put on the back burner as NASA is leaning toward
President George W. Bush’s announced desire to see Americans on the Moon
and Mars.

Hubble is slated to be replaced by the next-generation James Webb Space
Telescope, scheduled to be launched in 2014. The new observatory will have
a primary mirror that is 20 ft in diameter, compared to the Hubble's 8-foot
reflector.